A Brief Scientific Data Analysis of Philippine Eagle and a Brief Description of the Species

The Philippine National Bird and Its Size

Philippine Eagle (Pithecophaga jefferyi) is the largest eagle in terms of length and wing surface and is endemic to the Philippines as you can guess from its name. Their heights are up to 1m tall with wingspans up to 202cm and they weigh up to 8.1kg (Ferguson-less et al 2001). Since the family Accipitridae tends to indicate reversed sexual dimorphism, Philippine Eagle is no exception (Ferguson-less et al 2001). That means females are larger and therefore males are smaller.

The Name “Monkey-eating Eagle”

They prey on flying lemurs, flying squirrels, civets, snakes, hornbills, bats, and even monkeys(Ferguson-less et al 2001). So they are sometimes called monkey-eating eagle. You can see Philippine Eagle holding a monkey’s tail in its bill and flying in BBC Wildlife Specials, Eagle: The Master of the Skies (narrated by legendary Sir David Attenborough). Monkeys are incredible animals because of their intelligence and agility for climbing and jumping. It is hard to imagine such huge birds catch super agile monkeys and kill them during flight. In fact, eagle’s gripping force is bone-crashing (Olsen 2005). Such a phenomenal power is equipped with incredible talons.

Conservation Status

They are among the rarest vertebrates in the world. Its conservation status is surprising that such incredible animals are on the verge of extinction. As a matter of fact, they’ve been classified as Critically Endangered (CR, meaning population reduction is greater than 80% so unless we change the course, we are very likely to lose the species) for 23 years (since 1994) (IUCN 2015). Additionally, the population trend is still decreasing according to International Union for Conservation of Nature (IUCN) (IUCN 2015).

Estimated Population

During the 1970’s estimated population was within 200-400 individuals with the maximum of 590 individuals in Mindanao area which is the main habitat of the target species (Kennedy 1977,1981,1985). What about the latest information? I have found that in 2015 the maximum is estimated at 233 pairs (if you simply double, 466 individuals), and the minimum is estimated at 82 pairs (roughly 164 individuals) so roughly 164-466 individuals in Mindanao area (IUCN 2015)? Of course not. But this remains unclear even in the most-studied area.

In Addition, 6 pairs and 2 pairs have been observed in the areas of Samar and Leyte, and unknown population (at least one pair) but very few population is in Luzon area (IUCN 2015). To sum up, there likely to be 90-250 pairs, or 180-500 mature individuals, which roughly equating to 250-750 in total (not in Mindanao area but in the country) (IUCN 2015).

It is strange because the IUCN 2015 report says the species’ current population trend is decreasing but if you look at the 1970’s scientific data, you will realise that there is a possible increase from 1970’s or the population size have been stable. Nonetheless, to me, this is due to difficulties to measure the population size in such densely forested areas (Tingay et al 2010), and thanks to recent technology, scientists could do field research much more effectively for the latest assessment.


Habitat loss and fragmentation are the main factors of the population decline. The average of deforestation in the Philippines is estimated at 134,210 ha/year between 1934 and 2010 (Senate Economic Planning Office 2015). In 1934 there were 17,000,000 ha of forest areas in the country, however, only 6,800,000 ha of forest areas remained in 2010 (Senate Economic Planning Office 2015, original source from World Bank 2009 and Forest Management Bureau 2012). The Philippine Eagle’s potential habitat was decreased by 60% in 76 years. The loss of the forest area was due to logging including illegal one and construction of large road networks (Liu et al 1993). Moreover, most remain lowland forest is leased to logging concessions (IUCN 2015). Ecological study suggests that each pair of the eagles covers an average of 133 square kilometres (13,300 ha) (Bueser et al 2003). Therefore, large scale reforestation is required in order to preserve the species. In my opinion, however, I cannot blame illegal logging because poor people (12-15 million) rely on the biodiversity of the country (Senate Economic Planning Office 2015), for example, trees for fuelwood and animals for food in order to survive. In other words, those people whose livelihoods depend on the dipterocarp forest. I think I am seeing a conservation dilemma here. You cannot just take priority over neither the environment nor poor people without concrete evidence to suggest what you do. I am not philosophical enough to discuss further and also topic is beyond this writing. Nevertheless, there is no doubt that human management have caused the Philippine Eagles’ population decline as many parts of habitat have been chopped down and have been fragmented.

Additional threats include uncontrolled hunting, possible pesticide accumulation (biomagnification or bioamplification, further research is needed to clarify), accidental capture in traps intended for wild pigs and deer, and mining applications (IUCN 2015).

Positive Facts and Conservation Efforts

There are always negative facts and positive ones. I would like to mention changes of directions which conservationists worked hard and made them visible with their passions for preserving the species.

In 1969 WWF (World Wildlife Fund, now World Wide Fund for Nature) urged the species protection, then the government declared the bird as protected, and established the Monkey-eating Eagle Conservation Program (Salvador et al 2006; Kennedy 1985).

After having ceased receiving support from the government, the group started as Philippine Eagle Foundation, which is a non-governmental organisation (NGO), in 1987 (Salvador et al 2006).

Conservation efforts include ecological field research using radio telemetry, DNA analysis, captive breeding and releasing program (IUCN 2015), conservation education (working with over 1,700 teachers in 579 schools throughout the archipelago) (Salvador et al 2006), and reforestation with a mean of 251,254 ha/year between 2011 and 2014 (the rate is higher than deforestation)(Senate Economic Planning Office 2015).

In 2015 a survey team found first active nest in Luzon area. Then slash and burn agriculture is regulated by a local ordinance in the forest which the active nest was found (Ranada 2015; IUCN 2015).


As IUCN has classified the Philippine Eagle as CR (IUCN 2015), land management and interventions should thoroughly be planned. It seems hard to obtain ecological data as population is so few. Nevertheless, further research is required to apply effective interventions and to obtain genetic information for effective captive breeding and releasing program (Miranda et al 2008).

Other approaches include poverty alleviation (Salvador et al 2006), biodiversity offsets, sustainable development and conservation education. These ways of approaches are important to long-term conservation (Sutherland 1998). These all activities have to be done by humans not only for ourselves but also for future generations. In many ways, conservation requires a lot of money (Jepson et al 2010). Therefore, perhaps, financial support will be extremely helpful.

You Can Save the Philippine Eagle

You can save the Philippine Eagle by donating online. Visit the Philippine Eagle Foundation Website today! You can make a donation as small as US$2.

Please note that I don’t receive any money from the foundation. I personally recommend you to do so.


  • Ferguson-less J. and Christine D. A. (2001). The Raptors of the World. Houghton Mifflin Company.
  • IUCN (2015). The IUCN Red List of Threatened Species: Pithecophaga jefferyi
  • Salvador D. J. & Ibanez. J. C. (2006). Ornithological Science: Ecology and Conservation of Philippine Eagles (downloaded from Philippine Eagle Foundation Website)
  • Salvador I. D. (unknown). Holistic Strategies to Save the Philippine Eagle (downloaded from Philippine Eagle Conservation Foundation Website)
  • Senate Economic Planning Office (2015). Philippine Forest at a Glance.
  • Ibanez C. J. (2007). Philippine Eagle Breeding Biology, Diet, Behaviour, Nest Characteristic, and Longevity Estimate in Mindanao Island
  • Bull. W. (2003). Notes on the Breeding Behaviour of a Philippine Eagle Pair at Mount Sinaka, Central Mindanao (downloaded from Philippine Eagle Conservation Foundation Website)
  • Bueser G. L. L., Bueser K. G., Afan D. S., Salvador D. I., Grier J. W., Kennedy R. S. & Miranda H. C. JR. (2003). Distribution and nesting density of the Philippine Eagle Pithecophaga jefferyi on Mindanao Island, Philippines: What Do We Know After 100 Years? (downloaded from Philippine Eagle Conservation Foundation Website)
  • Philippine Eagle Conservation Foundation (unknown). Updates on the Nesting Biology and Population Status of the Philippine Eagle (downloaded from Philippine Eagle Conservation Foundation Website)
  • Kennedy RS (1985) Conservation research on the Philippine Eagle. Natl Geogr Soc Res Rep 18: 401–414.
  • Olsen P. (2005). Wedge-tailed Eagle. CSIRO Publishing.
  • Sutherland W. J. (1998). Conservation Science and Action. Blackwell Publishing.
  • Miranda Jr. H., Salvador, D. I., Bueser, G. L. (2008). Updates on the nesting biology and population status of the Philippine Eagle Pithecophaga jefferyi.
  • Ranada, P. (2015). First active Philippine eagle nest in Luzon found in Apayao. Rappler.
  • Jepson P., Ladle R. (2010) Conservation: A beginners Guide. Oneworld.
  • Kennedy, R.S. (1981). The air’s noblest flier. Filipinas J. Sci. Cult. 2: 33–48.
  • Kennedy, R.S. 1977. Notes on the biology and population status of Monkey-eating Eagle of the Philippines. Wilson Bull. 89: 1–20.
  • Tingay R.E. & Katzner T.E. (2010)  The Eagle Watchers: Observing and Conserving Raptors Around the World. Cornell University Press.
  • Liu S.D., Iverson L.R. and Brown R. (1993) Rates and patterns of deforestation in the Philippines: application of geographic information system analysis. In Forest Ecology and Management. 57: 1-16

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